CT selection for crowded board

Hi Bob,
I’m looking to install an Iotawatt across 11-12 circuits in a sub board that’s very tight on space.

There’s an 80A main breaker and a bunch sub circuits for lights (2x10A), power (3x16A), air conditioning (3x16A), oven (1x16A) and a shed (1x20A). Typical consumption is 200kWh/month in winter and 500kWh in summer. Typical maximum load would be 7-10 kVA with all the air-conditioning, oven, lights and appliances running simultaneously.

I’m planning on installing a 50A for the mains, the air conditioning group (4.8kW), and one for a future 5kW solar install. Is there a recommended 10/20A compact CT for the other sub circuits? I’m happy to solder up leads and jacks.

I’d like to monitor each of separately, but I’m not sure there will be space for 12 CTs n the board. Apart from grouping circuits, are there any other space saving tricks?

Cheers, Jon

CCHi Jon,

I’m guessing this is three-phase. I think you are looking for smaller, and not necessarily lower capacity CTs.

For split core, there are some available from both Echun (ECS0625) and YHDC (SCT006). Both 6mm opening and Neither is particularly good above 15A at 50Hz, but below that they’re fine. I don’t carry either one.

If you go solid core, you can get good 40A CTs in the HWCT-004 and CT08CL02. They are identical in every respect except the number printed on them. They come with two short leads, so need a cord and jack, and TVS diode to be safe.

OD 25mm ID 8mm width 13mm.

By contrast the 50A ECOL09 that I stock is

OD 26mm ID 9mm width 16mm

These have 1m cords, jacks and diodes and are UL listed.

PS. Better check the size of the 80A mains. The ECS1050 has a 10mm opening.

Thanks Bob,

It’s a single phase house, but the board is quite small. It doesn’t look like there’s much space saving to be had over the ECOL09. Might need to get a Tetris player instead of a sparky.

Picture of the board below. The single breakers are all 17mm wide. The top half of the board is typically circuit termination/earthing and loops back to the main breaker.
The vacant breaker slots will likely be used for solar and a potential electric hot water system in the future.

Without a picture of the actual wires, it’s hard to say. Safe to assume the wires coming from the breakers will be 17mm apart (-wire size). So a solid core can’t have a radius larger than that. The radius of the 50s is 13mm.

If they are more than about 32mm coming out of each breaker, then the CTs may be able to be staggered to get the clearance.